Grinding a torical section into a lens blank to optimal depth requires data relating to the selected spectacle frame size and shape. There are currently two systems in use which describe the size and shape of commercially available frames. The older method uses an orthogonal box approximation where a rectilinear region A.multidot.B based on horizontal and vertical frame dimensions A and B describes the smallest region which will circumscribe the perimeter of the frame, and a circular region ED describes the polar field of a vector which extends from the center of A.multidot.B to the outermost effective perimeter of the frame. A closed region C is generated by intersecting the rectilinear and circular regions, such that C=A.multidot.B.andgate.ED. The perimeter of C is then used as a first order approximation to the frame shape in minimum edge thickness calculations. A method more accurate than the first approach involves development of C from a spline fit tangentially to coordinates sampled regularly about the perimeter of the actual frame to be used. These coordinates are generally stored in conjunction with the size and style of the frame and maintained in a mass storage device for later use in lens optimization calculations. The symmetry assumptions made by the first system essentially insure that a lens blank will be ground to less than optimal depth and result in excessively thick spectacles when high powers are prescribed. The second system, although accurate, requires considerable information storage due to the large number of frame styles and sizes in popular use, and additionally requires that the database be regularly updated with new types before lens thickness optimization can be universally applied to all ophthalmic prescriptions.